General issues Change over time

Because mental processes and behaviour change as a child develops, it is not always clear whether the same diagnoses should be applied across the age range. Thus, a highly aggressive toddler may throw himself screaming onto the floor in daily tantrums, whereas a highly aggressive teenager may assault elderly people and rob them. Do they suffer from the same disorder? ICD-10 holds that they do—both meet criteria for conduct disorder, which is defined in terms of antisocial behaviour that is excessive for the individual's age, and that violates societal norms and the rights of others. DSM-IV on the other hand has two separate diagnoses, oppositional-defiant disorder for the younger case, and conduct disorder for the older. However, as both diagnoses have similar correlates and there is strong continuity from one to the other, the validity of the division is questionable. Yet current adult psychiatric schemes have no diagnosis at all to apply to antisocial behaviour, unless it is part of a personality disorder.

The extent to which adult criteria should be applied to children requires good empirical data. In the case of obsessive-compulsive disorder, the phenomenology is remarkably similar in childhood, so there is not a problem. However, for depression the picture is rather different. Currently, ICD-10 and DSM-IV have few emotional disorder categories specific to childhood, and they are mostly subtypes of anxiety. Mood disorders are diagnosed according to adult criteria, with the consequence that surveys of depression find prevalence rates around zero under 8 years of age. Yet there are miserable children who cry frequently, say they are unhappy, look sad, and are withdrawn. However, they usually sleep and eat reasonably well, and their mood fluctuates during the day, with spells when they sometimes appear more cheerful. Should they not be allowed a diagnosis? ICD-9 had a category for 'disturbance of emotions specific to childhood and adolescence, with misery and unhappiness', and Puura et al.(4) have shown such children suffer impairment. Follow-up studies of prepubertal children referred with this picture showed a moderately increased risk of adult-type depression later on, whereas adolescents with depressive symptoms had a higher risk of adult depression. (5) Genetic studies show that symptoms of depression in prepubertal children are predominantly due to environmental influences, whereas after puberty genetic influences become more important/6,) This example shows that misery in younger children has some phenomenological features and external correlates in common with adult depression but also some differences, which makes a comprehensive yet parsimonious classification system all but impossible to achieve.

Autism is a developmental disorder that manifests itself in early childhood and affects the functioning of the brain, primarily in the areas of social interaction and communication. Children with autism look like other children but do not play or behave like other children. They must struggle daily to cope and connect with the world around them.